The present invention relates to a negative type resist composition which is suitable for lithography process for manufacturing semiconductor integrated circuits using deep ultra violet ray, including eximer laser beam, electron beam, X-rays or radiation, and the like.
In recent years, quarter-micron pattern formations have been demanded with the increase in the integration level of semi-conductor integrated circuits. Particularly, the eximer laser lithography has attracted attention because it enables producing 64 M to 256M DRAM (dynamic random access memory). As a resist suitable for such eximer laser lithography process, a resist utilizing the chemical amplification effects of an acid catalyst, generally called chemical amplification type resist, has been proposed and is putting in the practical use. For example, in the negative working chemical amplification type resist, an acid is generated from an acid generator by the action of high-energy radiation such as electromagnetic waves, and the solubility of a part exposed to a high-energy radiation of an alkali-soluble resin in an alkaline developing solution is reduced by cross-linking and hardening by the action of the generated acid and a cross-linking agent. On the other hand, the acid does not generate in a part that is not exposed to a high-energy radiation and thus the solubility in the alkaline developing solution is maintained. By such a mechanism, a negative working pattern is obtained by a series of treatments, i.e., a formation of a resist film, an irradiation for patterning and an alkaline development
The profile of a resist pattern is desirably closer to a rectangle because it has an influence on the accuracy of fine working.
Further, in the lithography using the chemical amplification type resist composition, post exposure bake is generally carried out in order to promote chain reactions using the acid generated by exposure as a catalyst. However, if sensitivity changes caused by fluctuations of post exposure bake temperature is large, the pattern dimension is susceptible to effects of temperature deflection or non-homogeneity of temperature of the bake equipment. Therefore, the sensitivity changes caused by fluctuations of post exposure bake temperature and the pattern dimensional changes at the same exposure amount are desirable to be smaller. However, in the conventional chemical amplification negative type resist, the profile at the pattern top section tended to be rounded and the sensitivity change caused by fluctuations of post exposure bake temperature tended to be large.
In the chemical amplification type resist, it is general practice to add the basic material to prevent deterioration due to inactivation of the acid associated with time passage from exposure to post exposure bake, that is, caused by standing after exposure. Attempts have been made to improve the pattern profile by selecting the basic material in this event. However, adding general basic materials which have been popularly adopted resulted in unsatisfactory effects or degraded the sensitivity or resolution, or caused sensitivity changes due to post exposure bake temperature fluctuations. Therefore, it has been desired to solve these problems.
It Is an object of the present invention to provide a negative type resist composition which has excellent pattern profile, small temperature dependency of the pattern dimensions after exposure, and achieves both excellent sensitivity and resolution. The inventors of the present invention have made extensive researches to achieve the object, and found that excellent performance can be obtained by compounding a specific basic material to the negative type resist composition comprising alkali soluble resin, acid generator, and crosslinking agent. Based on this finding, the present invention was completed.